As the game progresses, players pick up more gear and job abilities that begin to change party dynamics. At lower levels, mages can be damage dealers, nearly anyone with provoke can tank and often, one healer is all that's needed to keep the tempo going. In the mid-levels, parties still have lots of flexibility in who tanks, DDs, heals, etc. However, jobs begin to perform better when playing to their strengths.
Around level 55, many mid-level parties will be held in the ToAU areas. These parties tend to be TP burn parties. As players get closer to level 75, TP-burn parties tend to become more specialized. In mid-range levels, TP burns commonly consist of a tank, three damage dealers, a refresher and a healer. A TP-burn party is exactly as it sounds -- the tank and DD all melee the mob, and use their weaponskills individually, and as fast as possible, without worrying about skillchains.